Loud speaker construction



July 2, 1935. a. A. ENGHOLM 2,006,857

LOUD SPEAKER CONSTRUCTION Filed April 11, 1934 Patented July 2, 1935 UNITED STATES PATE N OFF [C E LOUD SPEAKER CONSTRUCTION Bernard A. Engholm,

assignor to The Rol Shaker Heights, Ohio, a Company, Cleveland,

1 Claim.

This invention relates to loud speakers and particularly to a device for locking the spider to the diaphragm housing, after the voice coil form has been centered with reference to the air gap. The fastening of the spider at such time is an important problem in the manufacture of loud speakers, because the anchoring must be sufiiciently tight to hold the outer edges of the spider, and yet the spider must be absolutely free from torsional and bending stresses at the completion of the tightening operation.

One form of a fastening device, which has been used for this purpose comprises a bridge piece that engages the spider and is fastened to the diaphragm housing by a threaded member. In such device, a pad has been stamped from the housing for providing a spider support. Experience has shown however, that the tolerances which are permissible in the assembly of a loud speaker necessitated such accuracy in the depth of the pad, that it has been diilicult to control it satisfactorily on a large stamping, such as that which is used for the diaphragm housing. The use of a pad however, is necesary, for the point of connection between the spider and the diaphragm is spaced an appreciable distance from the outer pole piece.

An object of my invention therefore, is to provide a construction wherein the pad may still be utilized for holding the spider, but in which the diificulty in maintaining exact tolerances in a large stamping is eliminated. In this connection, my invention also contemplates a construction wherein the spider must still be locked by means of a bridge piece, as heretofore described.

A further problem in connection with the manufacture of loud speakers is the supporting of the leads which extend from the voice coil to a terminal block on the diaphragm housing. Heretofore, such leads have been anchored at their inner ends to a convenient point on the diaphragm, near the outer end of the voice coil form, and conductors have extended from the points of connection at the diaphragm to the terminal block. The length of such conductors however, has proven to be undesirable, as they tend to dampen the action of the diaphragm, and thus reduce its efficiency.

A further object of my invention, therefore, 50 is to provide a support for such conductors that will still permit them to be attached to the diaphragm and to the terminal block, and which will materially shorten the unsupported length, and thus relieve the diaphragm of all retardation.

Referring now to thedrawing, Fig. 1 is aside elevation, partly in section, of a loud speaker embodying my invention, and taken on the line l-l in Fig. 2; Fig. '2 is an end view of a-speaker with part of the diaphragm broken away and showing the interior construction; Fig. 3 is a perspective view of part of the housing, and its associated spider support; Fig. 4 is a diagrammatic view on an enlarged scale showing the conductor support, and Fig. 5 is a section taken on the line 5-5 in Fig. 2.

The loud speaker, which I have shown is of the electro-magnetic type, which has a field coil 20, an inner pole piece II, and outer pole piece 2, a voice coil I3, a voice coil form M, a diaphragm IS, a diaphragm housing l6, and a spider H. The spider is fastened at its inner edge preferably by cementitious material to the diaphragm adjacent the point of its connection to the voice coil form, and is adjustably fastened at its outer edges by a device, which is made in accordance with the present invention.

Such device includes a pad, which is shown in Fig. 3, as having a base portion 20, which is substantially triangular in shape, and which has a raised portion 2| that is stamped therefrom and that is adapted to provide a bearing surface for the spider. The pad is rigidly fastened to the housing, as by rivets 22, and is provided with spaced openings 23, 24 and 25 that are preferably in alignment, and that extend entirely therethrough. The opening 24 is larger than the openings 23, and is adapted to receive a threaded securing member 26, which in turn, as is shown in Fig. 1, extends through the housing and pad, and engages a threaded opening in the bridge piece 21. The bridge piece then may have tabs 28 and 29 which enter the openings 23 and 25, respectively, and which cooperate therewith to hold the bridge piece against rotation when the member 26 is tightened.

There are two bridge pieces illustrated in Figs.

1 and 2, and each act to clamp the spider against the raised portion 2| of the pad. Inasmuch as the pad is a relatively small stamping member, it can be accurately made, and can be readily varied to suit the requirements of different models of a loud speaker without changing the size of the housing.

The leads from the voice coil are shown, as being fastened to the diaphragm at 30 and 3|, and from such points, conductors 32 and 33 are extended to a terminal block 34. The block is usually fastened to the housing, and so the con- 5 ductors must be sufficiently loose to allow the necessary piston action of the diaphragm. Conductors 32 and 33 are usually made of braided wire, and the distance between the points of connection at the diaphragm and terminal block respectively is sufficiently long to set up a whipping action, while the diaphragm is in motion. The effect of such action is to impede the movement of the diaphragm, and so I pro vide an intermediate support for the conductors that will eliminate the action referred to, and still allow suflicient flexibility to permit freedom of movement of the diaphragm.

The preferred form of support, which I have devised comprises tabs 35 and 36 which extend laterally from the spider and adjacent one end thereof. Each tab has slots 31 and 38 therein through which the conductors may be looped, as is shown in Fig. 4. A convenient arrangement for retaining the conductors in position without requiring them to be rigidly connected to the spider is to extend the slots at right angles to each other, as in this way the material adjacent the slots provides an adequate support for holding the conductors against movement, after they have been threaded into place.

Furthermore,

this can be accomplished before the spider, and the associated diaphragm assembly is locked into place against the housing. Thus, the operator can readily determine by inspection the length of conductor between the spider and the diaphragm, and can allow sufiicient length to assure freedom of movement of the diaphragm.

While I have shown a preferred arrangement for carrying out my invention, it is to be understood that various modifications thereof may be utilized without departing from the spirit of my invention.

I claim:--

A spider support for a loud speaker, comprising a pad having a body portion that is substantially triangular in shape, and that has a raised seat adjacent one edge thereof, for providing a bearing surface against which the spider may engage, said pad having openings in the body portion and seat respectively for receiving a bridge piece and having an opening disposed between said body and seat openings through which a securing member may be extended for clamping the bridge piece to the pad.

BERNARD A. ENGHOLM. 

